Evaluation of in vitro antioxidant activity of bark extracts of Terminalia arjuna

To uncover the antioxidant and free radical scavenging activity, five different extracts ofTerminalia arjuna bark were examined. In the present study, the free radical scavenging potential of five extracts of the bark of Terminalia arjuna was assessed by measuring its capability for scavenging 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical, hydrogen peroxide radical, nitric oxide radicals (NO), as well as its ability in reducing power capacity assessment, cupric reducing antioxidant capacity, using appropriate assay systems compared to natural and synthetic antioxidants. Total antioxidant capacity, phenolic and flavonoid contents were determined spectrophotometrically. In DPPH free radical scavenging activity, the highest IC50 value was showed by methanol extract with a value of6.34 µg/ml followed by ethanol and petroleum ether having value of 7.76 and 25.63,respectively, as opposed to that of the scavenging effects of ascorbic acid and butylated hydroxytoluene (BHT) of 5.698 and 8.816, respectively. Methanol extract showed highest activity having IC50 value of 14.436 and 25.184 μg/ml in hydrogen peroxide and nitric oxide scavenging assay, respectively. All the five fractions showed good reducing power and cupric reducing capacity with increasing concentration again taking methanol extract to the top position. The methanol extract yielded 817.488 ± 8.108 mg/g gallic acid equivalent phenolic content and 199.122 ± 8.282 mg/g Quercetin equivalent flavonoid content that was highest among five extracts. Methanol extract of T. arjuna was found to possess the highest total antioxidant capacity (415.925 ± 2.291) followed by ethanol (377.675 ± 1.889) mg/g Ascorbic Acid Equivalent, respectively. A linear correlation appeared between the total antioxidant capacity and the total phenolic contents of the extracts with good correlation coefficient (R2 = 0.891). n-Hexane and chloroform extract showed least activity in all the measures. The results obtained beacon that T. arjuna is a potential source of antioxidants and thus could prevent many radical related diseases. Key words: Terminalia arjuna, n-hexane extract, petroleum ether extract, chloroform extract, ethanol extract, methanol extract, in vitro antioxidant activity.